<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>TEST</title>
    <style>
html {
  font-size: 10pt;
}
.container {
  position: relative;
  border: solid silver;
  width: 40em;
}
.relpos-em {
  background: lime;
  position: relative;
  left: 20em;
  width: 20em;
}
.relpos-rem {
  background: orange;
  position: relative;
  left: 20rem;
  width: 20rem;
}
.abspos-em {
  background: lime;
  position: absolute;
  left: 20em;
  width: 20em;
}
.abspos-rem {
  background: orange;
  position: absolute;
  left: 20rem;
  width: 20rem;
}
.hspace {
  height: 5em;
}
    </style>
  </head>
  <body>
    <h2>root font-size: 10pt;</h2>
    <div class="container">
      <div class="test relpos-em">
        position: relative;
        left: 20em;
        width: 20em;
      </div>
      <div class="test relpos-rem">
        position: relative;
        left: 20rem;
        width: 20rem;
      </div>
      <hr>
      <div class="test abspos-em">
        position: absolute;
        left: 20em;
        width: 20em;
      </div>
      <div class="hspace"></div>
      <div class="test abspos-rem">
        position: absolute;
        left: 20rem;
        width: 20rem;
      </div>
      <div class="hspace"></div>
    </div>
  </body>
</html>
